1. Field of the Invention
The present invention relates generally to optical aperture mechanisms and more particularly to a mechanism including multiple selectable and rotatable pattern apertures or transparent liquid crystal displays.
This application is related to copending application Ser. No. 07/224,438 filed Jul. 26, 1988, now U.S. Pat. No. 4,891,738, issued Jan. 2, 1990, entitled "Selectable Aperture Module", assigned to the assignee of the present invention.
2. Discussion of the Prior Art
Conventional theatrical and display lighting systems have used various types of optical filters which are removably insertable into light beams to modify the distribution of light in the projected beam. U.S. Pat. No. 2,214,728 describes a color wheel which includes several optical filters and which is rotatable to position a selected filter across a beam of light. The several filters have equal areas with uniformly dense coloring and do not produce different shapes in the projected beam of light.
U.S. Pat. No. 1,449,122 describes a kaleidoscope projector including several hollow tubes that are lined with different numbers of mirrors and supported in a frame which is rotatable to position a selected tube around light in a beam along an optical axis. Tube rotation gears are used to turn the selected tube of mirrors to spin the kaleidoscopic beam around the optical axis. However, the rotatable mirror tubes cannot stencil patterns into the beam, which requires a pattern aperture in a focal plane of the projector. The beam of light may be conventionally patterned by a strip of film scrolled across the beam between opposite side spools.
U.S. Pat. No. 3,030,856 describes a kaleidoscope projector which forms variable apertures using a pair of main disks each supporting a plurality of smaller disks around its periphery. Each smaller disk has translucent apertures spaced regularly around its own periphery. The main disks and each of the smaller disks are simultaneously rotated to continuously, and practically uncontrollably, vary the effective aperture shape and the pattern of light in the beam projected from the kaleidoscope.
U.S. Pat. No. 4,232,359 describes an illumination system including a plurality of shutters having edges or patterns of desired shapes, one or more of which may be manually inserted into, and remain fixed at a respective location in, a beam of light.
U.S. Pat. No 4,460,943 describes a light projector including a disc which has a number of openings for mounting "gobos" (stencils for light) and which is rotatable to insert a selected gobo into the focal plane of a beam of light.
Liquid crystal displays (LCD) have been used in a wide variety of different projection and display applications. U.S. Pat. Nos. 4,195,915 and 4,443,819 describe using a reflective type LCD to project television images. U.S. Pat. Nos. 4,222,641, 4,294,524 and 4,368,963 describe a projector system which projects light through a stationary transparent LCD onto a cinema screen. U.S. Pat. Nos. 3,722,988, 3,844,650, 3,895,866, 4,671,634, 4,722,593, 4,756,604 and 4,345,258 all describe various types of transparent LCD projectors where the LCD is fixed in a stationary position.
U.S. Pat. No. 4,568,080 describes a transparent LCD display in which the LCD may be placed in a number of different operative positions. However, once the LCD is affixed in a particular position it may not thereafter be moved to a different position without dismantling the display system. Hence, none of the above prior art teaches or suggests automatically positioning the LCD in front of a light beam or selectively interchanging that LCD with a number of mechanically formed apertures so as to controllably vary the projected pattern of light.
U.S. Pat. Nos. 4,693,557 and 4,613,207 describe a motion picture projector in which a continuous strip of transparent liquid crystal material capable of temporarily storing charge is utilized to create a series of picture frames for projection onto a screen. As each frame is created and projected, it is moved out of the way and the next frame is moved into the projection optics for projection. Images are created on the liquid crystal material by passing the liquid crystal material beneath a dynamic electrode, formed in the shape of a roller, which charges selective portions of the LCD so as to form the desired images. In both of these patents, no provision is made to project light onto the screen in any other manner than through the liquid crystal material.